The major objectives of this research proposal are to study regulation of the synthesis, storage and secretion of parathyroid hormone by the glands of animals and man both in vitro and in vivo. The project includes the use of "perifused glands" in vitro to study factors regulating parathyroid hormone secretion. From observations made in the in vitro systems concepts that are relevant to secretory control in animals and man will be developed. The project involves the study of animals with parathyroid transplants and patients who have received therapeutic transplantation of the parathyroid glands for primary or secondary hyperplasia. Blood sampling near the site of hormone production facilitates the study of parathyroid physiology in vivo because it eliminates the complexities normally encountered from parathyroid hormone fragments in peripheral blood.